Answer to Question #274830 in Electrical Engineering for MD HUMAYAN KABIR

Question

Compare Ge diodes to similarly structured and doped Si diodes for the following 

(give reasons): 

(1) Reverse saturation current 

(2) Avalanche breakdown voltage

Answer 1

Diodes are two-terminal electronic devices / components that functions as a one-way switch i.e., they allow current to flow only in one direction. These diodes are manufactured using semiconductor materials like Silicon, Germanium and Gallium Arsenide.

The two terminals of the diode are known as Anode and Cathode. Based on the potential difference between these two terminals, the operation of diode can be classified in two ways:

• If anode has higher potential than cathode, then the diode is said to be in Forward Bias and it allows current to flow.
• If cathode has higher potential than anode, then the diode is said to be in Reverse Bias and it doesn’t allow current to flow.

Different types of diodes have different voltage requirements. For Silicon Diodes, the forward voltage is 0.7V and for Germanium diodes, it is 0.3V. Usually, in Silicon Diodes, the dark band on one end of the diode indicates the Cathode terminal and the other terminal is anode.

One of the main application of Diodes is Rectification i.e., to convert AC to DC. Since diodes allow current to flow only in one direction and blocks current flow in the other direction, diodes are used in reverse polarity protector and transient protector applications.